1. Temperature Compensation
The strain gauge would change its resistance with respect to the temperature.
Gauge resistance is affected by many reasons in which temperature plays an important role.
Total indicated strain= Mechanical Strain Apparent Strain

2. -Contn… When temperature increases Gauge grid will elongate ∆𝑙 𝑙 =∝.∆𝑇
Base material mounted on gauge will elongate
∆𝑙 𝑙 =β.∆𝑇
Resistance of the gauge will increase
∆𝑅 𝑅 =γ.∆𝑇

3. -Contn…
The combined effect of these three factors will produce a temperature induced change in resistance of the gauge as
∆𝑅 𝑅 = 𝛽−𝛼 ∆𝑇.𝐹+𝛾∆𝑇
α= Thermal coefficient of expansion of the gauge material
β= Thermal coefficient of base material
γ= Thermal coefficient of gauge material
F= Gauge factor

4. In order to prevent significant errors due to “Temperature Compensation” current available methods are
Compensating dummy gauge
Self temperature compensated gauge
Compensation by Dissimilar gauge
Compensation by Similar gauge
Compensation by Computation

5. Compensating Dummy Gauge
This is the earliest form of temperature compensation technique.
The active gauge is connected with a dummy gauge to balance out the unwanted temperature induced resistance change.
The dummy gauge is identical to active gauge mounted on unstressed specimen exposed to same thermal environment.

6. Disadvantages
This method is failure if temperature variations are not uniform in both the gauges.

7. Self-Temperature Compensated Gauge
The term temperature compensated denotes that change is resistance due to temperature is zero.
This method is successful only when materials having specific value of thermal expansion coefficient.
It must be 0-25 ppm/Deg C

8. This can be achieved by two methods
In First method- Self temperature Compensation is created by altering the temperature coefficient of grid material.
So that when mounted on materials having a certain thermal expansion coefficient thermal expansion will be low.

9. -Contn..
The Second method includes forming a grid with two different lengths of gauge wires in series so that resultant apparent strain is zero.

10. Compensation by Dissimilar gauge

11. -Contn
The gauge in the first arm should have relatively small temperature effect in same direction
In the Second arm series and shunt resistance are connected in series so that the temperature effects of two arms cancel each other.

12. Advantages
This method is more successful than Self temperature compensated gauge because of relative resistance of the filament is not critical.
Compensation over a greater temperature is easily achieved.
Disadvantages
At higher temperature, Value will not be known accurately.

13. Compensation by Similar gauge
Best Suitable method for Unpredictable and Predictable Effects of temperature.
It is achieved by connecting by two similar gauges in series like Wheatstone Bridge Circuit.
One gauge connected in direction of maximum principal strain.
Other gauge in the direction of minimum principal strain.

14. Advantages
It can easily eliminated hydrostatic component of stress from reading.
Shear component of stress can be easily predictable.
Best suited method if the direction of principle strain is known.

15. Compensation by Computation
By knowing the temperature characteristics of Strain gauge and the base metal, temperature correction can be easily calculated theoretically.